Cyclical, pertaining to a periodical space of time marked by the recurrence of something peculiar.
Data (pl. of datum), a ground of inference or deduction.
Debris (dā-breé), fragments detached from rocks, and piled up in masses.
Demi-relief, the projection of one half the figure beyond the plane from which it rises.
Dendrites, a stone on which are tree-like markings.
Devonian, the geological age between the Silurian and Carboniferous.
Diluvium, the time when the glacial beds were deposited.
Diorite, a tough rock, in color whitish, speckled with black, or greenish black.
Dolichocephalic, a skull whose diameter from the frontal to the occipital bone exceeds the transverse diameter.
Dorsal, the name given to the second division of the vertebræ.